INVESTIGATING THE THERMAL COMFORT CONDITIONS IN AN … · 2017-05-24 · thermal comfort index and they do not consider the thermal sensation scale. Furthermore, Farghal (2011) set

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Journal of Engineering Sciences

Assiut University

Faculty of Engineering

Vol. 45

No. 3

May 2017

PP. 344 – 359

INVESTIGATING THE THERMAL COMFORT CONDITIONS

IN AN EXISTING SCHOOL BUILDING IN EGYPT

Hala Hammad, Morad Abdelkader, Ahmed Atef Faggal

Depart. of Architecture, Faculty of Engineering, Ain-Shams University Cairo, Egypt

Received 30 November 2016; Accepted 10 January 2017

ABSTRACT

This paper investigates, using software modeling and numerical simulations, the annual thermal

performance of a public primary school in Cairo governorate in Egypt. This investigation identifies

how much time the students achieve thermal comfort in their classrooms during the whole academic

year. It is also considered as an attempt to magnify the need for solutions that can enhance thermal

comfort in classrooms. As a support to our computer modeling and simulation, this paper preforms

also an analysis to the thermal comfort indices via field measurements for the internal temperatures

and humidity of a classroom by using the Elitech UR4HC temperature–humidity data logger. The

field measurements have taken place in June 2016 for a whole school day from 8:30 am until 14:30

pm. Energy Plus simulation tool has been used utilizing its modeling interface Design Builder. The

numerical simulation proposed has considered the real construction aspects and parameters of the

classroom case study. Measurements validate the simulation results and ensure that the tool is

reliable to be used in the annual simulations, which is the main concern of this paper.

This paper presents, through annual building thermal-performance simulations, the forecasting for

the yearly mean indoor air temperatures, Predicted Mean Vote (PMV) model, discomfort hours, and

internal heat gain balance. Simulation results indicate the existence of a high level of thermal

discomfort during the whole academic year. The annual analysis also indicates around 45% of the

working hours are exceeding the maximum limit of the comfort temperature range. Furthermore, the

results present a high level of average annual internal heat gain balance throughout the academic year.

As a main contribution of this paper, the simulation results draw attention to the importance of

integrating new passive cooling strategies or energy efficient cooling systems in order to: stabilize

the indoor temperature, increase the students’ thermal comfort and decrease the internal heat

balance for enhancing the thermal performance of school buildings in the future.

Keywords: thermal comfort, discomfort hours, Predictive Mean Vote (PMV), overheating hours,

internal heat gain, cooling load

1. Introduction

Educational buildings are one of building types necessarily of great interest when one

consider the potential links between building performance, thermal comfort, and energy

consumption [1]. The reason is that the students spend long times in their classrooms,

thereby, a good indoor environment can help in optimizing conditions for students’

performance. Classrooms thermal performance not only affects the students’ health and

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Hala Hammad et al., Investigating the thermal comfort conditions in an existing school building…...

comfort, but also it affects the students’ learning efficiency and productivity [3]. Recently,

most of new school buildings have been constructed without considering students’ thermal

comfort. Many researches show that as temperature increases above 26°C, students’

performance decreases significantly [3, 4 and 5].

According to literature, indoor thermal comfort has been widely investigated for

different types of public spaces. For educational halls, there are a considerable amount of

publications that have been considering the college students’ thermal comfort and lecture

halls thermal performance. A. Abdallah (2015) analyzed the indoor thermal comfort and

energy consumption inside a large educational hall at the Faculty of Engineering, Assiut

University; the research was aiming at determining the acceptable operating temperature

for students’ comfort [3]. His results show that the indoor temperature exceeds 28°C in

summer months and is far from the 90% acceptable comfort range with a high PMV range.

K. M. Dewidar et al. (2013) monitored the indoor temperature inside a large lecture hall in

Cairo University; they conducted measurements for temperature, relative humidity, and

wind speed for 30 points inside the hall [9]. They concluded a high level of thermal

discomfort and suggested to operate passive systems that could control temperature,

relative humidity and solar radiation. However, they do not compare their results with the

thermal comfort index and they do not consider the thermal sensation scale. Furthermore,

Farghal (2011) set an Adaptive Comfort limit for university buildings in Cairo through a

subjective field study of occupants in educational halls in three Universities in Cairo [12].

On the other hand, only few studies in the literature investigate the thermal comfort

criteria within school buildings in Egypt. In this context, Gado and Mohammed (2009)

investigate the thermal comfort criteria from the subjective view of occupants and through

measurements of temperatures during May month. This has been carried out inside primary

governmental schools in AL-Minya governorate in Egypt [10], [11] and [13]. Their Results

indicate that internal air temperatures of all the case studies exceeded the comfort

temperature for most of the time and average PMV across the case studies was 1.7 which

indicates that the majority of the occupants would feel unpleasantly warm. In addition,

A.A. Saleem et al. (2014) examined the thermal performance of a public primary school in

Assiut city, Upper Egypt [14]. Their findings indicate a high level of thermal discomfort.

The average measured values of both the PMV and PPD inside the classrooms were 1.17

and 38.86% respectively. Moreover, it indicates that there are a strong relation between

indoor comfort conditions and outdoor temperature.

It is clear from the literature review, and up to the knowledge of the authors, that all

researches investigate the students’ thermal comfort for a maximum duration of one month

and do not consider the annual thermal performance analysis. Hence, there is not any

research that investigates the thermal performance of school buildings in Cairo for a

complete year of investigation. Therefor this paper comes to fill in this gap and

investigates, through numerical simulations and computer modeling, the annual thermal

performance of a governmental primary school building in Cairo governorate. The results

of this paper monitor the thermal comfort criteria and internal heat balance, during a

complete academic year, in order to draw the attention to the need for cooling systems that

can be integrated to future school buildings to achieve thermal comfort.

In order to briefly summarize the structure and analysis of this paper, it is important to

highlight the problem definition of this research and its main objectives:

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JES, Assiut University, Faculty of Engineering, Vol. 45, No. 3, May 2017, pp.344–359

Problem definition: indoor-spaces in school buildings have been rarely studied for a complete

yearly thermal performance compared to other buildings, e.g., offices and residential buildings.

Main objectives: The main objective of this paper is to evaluate the annual thermal

performance of a classroom as a base case to all classrooms in order to monitor the thermal

comfort criteria, number of discomfort hours, and internal heat balance throughout a whole

academic year. This is done to be able to develop more energy efficient systems and

sustainable design guidelines for future school buildings in Cairo.

This paper is organized as follows: Section 1 is this introduction. Section 2 concerns

monitoring and simulating the thermal comfort indices of an existing governmental school

building in Cairo in a perfect summer day. Moreover, it estimates the space thermal

performance throughout an academic year through annual simulations. Section 3 analyzes

the annual simulation results by evaluating the mean indoor air temperature, the predictive

mean vote model, the number of discomfort hours and the internal heat balance. Finally,

Section 4 is the conclusion of this work and recommendation for future work.

2. Methodology

2.1. Case study monitoring

This research studies the human thermal comfort criteria inside Taba public primary school

in Cairo, Egypt. The school building is consisting of 32 classes, it was built in 2001. Field

measurements took place during June 2016, in a single selected classroom. Fig. 1a presents the

northern elevation while Fig. 1b presents the southern elevation of the school building.

Taba Public School (now its name is changed to: the Martyr Colonel Hisham Al-Deen Abd

Al-Aziz School) is located in Nasr city, on Makram Ebaid Street. The coordinates of the school is

exactly 30.0276° N and, 31.2101° E, as depicted in the Google map and satellite capturing in Fig.

2. The site is surrounded by medium rise residential buildings. Its total area is about 450 m²,

consists of four stories each story is 2.90 m height. The building represents a single sided U-

shape form prototype of public school buildings; see Fig. 3 for more details about the floor plan.

Fig. 2. Taba primary school site location in Nasr city region in Cairo

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Fig. 3. Typical floor plan of Taba governmental primary school and the selected reference case classroom

The classroom under investigations is located in the second floor with a total flat area of

38.4m². The classroom contains three glass/sectional-aluminum windows, each is

2.8mx1.3m. Two of these windows are pointing to the south and one to the north. The room

is furnished with 3 rows of seats/desks; each row contains 7 seats/desks, i.e., a total number

of 21 seats/desks. Every wooden seat/desk carries 2 students; thus, the total number of

students is 42 students. Additionally, it contains one more wooden desk/chair for the

teachers; see Fig. 4 for more insights about the classroom internal furniture. The room has

internal dimensions of 8m × 4.8m × 2.9m (length × width × height). It contains one external

wall facing south. The northern wall is overlooking on an outdoor corridor facing the north

orientation, the ceiling and the floor are not directly exposed to the outdoor environment.

Fig. 4. Classroom interior views

The school construction is monitored as conventional construction building materials.

The external walls are of most common wall systems which consist of 25cm brick with

plaster finishing. The floor construction consists of 15cm reinforced concrete finished with

mixture-marble tiles, and the internal partitions consist of 12cm brick with a 2cm plaster

coating. As mentioned before, the south façade has two windows each of 2.80m × 1.30m

(length × height), while the northern façade has one window of 2.80m × 1.30m (length ×

height) of single glazing with no shading devices and it is naturally ventilated with no fans.

2.1. Measurements and data recording

The equipment used for measuring and recording the classroom indoor temperatures

and humidity is the Elitech tempreture–humidity data logger (model URC-4HC) [16]. The

spot of measurements was on the student’s middle desk at a height of 65cm from the

ground, as shown in Fig.5. The actual measurements take place every 1-minute intervals

the measurements are though averaged and saved every 10 minutes. Also, the data logger

was carefully placed to avoid any unnecessary impact, such as direct sunlight.

Measurements took place on the 22nd

of June, as it has been selected as a typical summer

day which represents extreme hot conditions. Measurements have taken place from 8:30am

until 2:30pm every 10 minutes.

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Fig. 5. Position of the data logger on the desk in the middle of the room

For the outdoor measurements we use an identical device similar to the one used for the

indoor. An outdoor sensor was connected to the device from the nearest window in the classroom

at the second floor level. The measurement values are presented in the next section, where a

relationship between the indoor conditions and the occupants’ thermal comfort is demonstrated. It

is worth to mention that during this measurements day, the students’ capacity was about 30 % of

the normal capacity in the classroom due to low capacity of summer courses in June.

2.1.1. Air temperature As stated before, the air temperatures and humidity, during the time interval from 8:30am

until 2:30pm in the selected classroom, is averaged every 10 minutes; the outdoor temperature is

measured with the same manner. Figure 6 presents a comparison between the indoor and outdoor

temperature variations monitored throughout the whole school day hours mentioned before.

The measured values clearly show that the temperatures inside the classroom, during

this day, are ranging from 27.5°C at the early morning, about 31°C during that daytime,

and a maximum of 33.5°C at the end of the school day. However, the Adaptive Comfort

Standard (ACS) (based on [6]) in this case is calculated to be in the range of 23.5-28°C,

which is less than the actual measurements.

Fig. 6. indoor and outdoor air temperature inside the classroom throughout the whole school day

Thus, the measurements reveal that the mean indoor air temperature is raised by about

6ºC on average. This level of increase can lead to thermal discomfort conditions for

students. As referred to [6], one can see that the temperature level in this case is higher

than the range of human thermal comfort; though, the temperature on the early morning

(from 8:30am until 10:13am) was near to the comfort range. Moreover, the finding in Fig.

6 tells that there is a strong relation between the indoor temperature variations with the

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indoor one, where the difference between the outdoor and indoor temperature are almost

constant, i.e., about 4ºC, until the end of the school day. This mandates the urgent need for

finding solutions for improving the space thermal behavior.

2.1.2. Relative humidity Relative humidity measurements, recorded in Fig. 7, shows that the level of variation within

the classrooms is fluctuated between 34% and 56% over the monitored school hours with a

mean percentage of about 46.1%. In addition, the relative humidity was, on average, about

50% until 12:00 pm, and then it decreases slightly to reach 34% at the end of the school day.

Honestly speaking, the measured values are affected by a main reason which is this: the

measurement day is during the summer school courses period, i.e., is until 12:30pm and is not a

normal full capacity studying day (the students’ capacity in the classroom was about 30 % of

the normal full capacity). Thus, the measurements still indicate that the relative humidity is still

in thermal comfort range, according to SHRAE (35- 60 %) [6], it is expected that these values

are subjected to be increased if the classroom was of full school day with full capacity.

Fig. 7. Relative humidity inside and outside the classroom base case

2.1. Modeling and simulation

The author has selected the simulation tool Energy Plus (E+), version 8.2.0.024, with an

interface to the software modeling tool Design Builder (DB), version 4.2 [17]. The simulation

tool E+ has been selected since it is widely used in the scientific communities as a tool for

thermal and energy performance simulations. Additionally, it has been considered to be more

suitable for making realistic simulation models using very realistic architectural models and

facilitates the use of Energy Plus. The latter has been validated under the comparative Standard

Method of Test for the Evaluation of Building Energy Analysis Computer Programs

BESTEST/ASHARE STD [18]. In addition, it has been validated by Energy Efficiency and

Renewable Energy (EERE) program, U.S. Department of Energy (DOE). Moreover, Wael

Sheta et al. (2010) have validated the Design Builder modeling tool (using Energy Plus

simulation environment) in Egypt, specifically for Cairo climate [18]. They concluded that this

combination of tools is a very satisfactory and reliable simulation package for investigating

sustainability and thermal performance analyses. Similarly, this paper investigation through

DB-E+ modeling and simulation testing was carried out in summer during the calendar year

2016, excluding August, which is the school annual vacation.

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2.3.1. Climatic features and weather data file of greater Cairo region The Egyptian Typical Meteorological Year (ETMY), the International Weather for

Energy Calculations (IWEC) and Köppen classified Cairo climate as a hot semi-arid

climate with a hot to extremely hot dry summer and mild to warm wet winter [14].

According to the reports published by the EMA (Egyptian Meteorological Authority),

precipitation in Greater Cairo Region is 0.00 mm/day in summer and 0.20–0.50 mm/day in

winter. Also reports recorded 40.0-45.0°C as the maximum temperature range in summer,

20.0-25.0°C as a maximum temperature range in winter, 20.0-25.0°C as a minimum

temperature range in summer, and 5.0-10.0°C as a minimum temperature range in winter.

E+ Weather data file represents the typical long-term weather patterns of the intended region.

The weather data file (for the year 2009) used for this study is (EGY_AL QAHIRAH_CAIRO

INTL AIRPORT_ETMY.epw); this file is an EnergyPlus weather file with the summary statistics

report (EGY_ALQAHIRAH_CAIRO INTL_ AIRPORT_ETMY.stat) [15].

2.3.2. Base case modeling Modeling and Analyses was performed for the same selected classroom, at which previous

measurements had been performed. Fig. 8 shows the school building model with exactly the

same construction and finishing materials. It also shows the case study location from the southern

elevation view. Fig. 9 presents the school visualization model made by Design Builder software

showing the sun path diagram at 13:00pm, on the 22nd

of June 2016. It presents a high rate of

solar radiations onto the southern elevation at the mid of the school day time.

Fig. 8. School Model South elevation (left hand side) North elevation

Fig. 9. School visualization model made by Design Builder software showing sun path diagram at 13:00, 22th June.

2.3.3. Input parameters and materials thermal properties For efficient modeling and simulation of the school building, one should consider the

existing construction materials and real parameters of the building to be applied to the

computer modeling. As the thermo-physical properties of wall materials can affect the

building’s energy performance [7]. The Simulation input parameters and limitations based on

the onsite data collected are shown in details in Table 1. It is assumed that the materials

properties are constant during the simulation time. Table 2 considers the various layers in the

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building envelope starting from the outermost layer to the innermost layer, with their thermo-

physical properties.

Table 1.

Simulation input parameters in Design Builder E+ tool

Element Data

Space dimensions 8.00 length × 4.80 width × 2.90 height

Openings

orientation

two openings South orientation and a door on northern elevation

Openings

percentage

40 %

Opening dimensions 2.80 length x 1.30 height

Internal blinds Non

External shading Non

Lighting 18 fluorescent lamps with a standard intensity of 450 lux

Classroom capacity 24 desks

Occupancy pattern 1.12 person/m² in normal school days

For June and July, in summer courses, occupancy rate is about 0.5person/m²

Considering the one day-simulation 22nd

of June: the real occupancy

pattern was 0.35 person/m²

Working time Sunday to Thursday day, between 8:30 am until 2:30 pm

For June and July, in summer courses, the school days is from 9:00am until 12:30pm

For the one day- simulation 22nd

of June, the school day started from

9:00am until 12:30pm

Annual vacation August

Metabolic rate 0.75

Clothing 0.3 clo.

Holidays 2 days / week

HVAC template No active cooling systems

Natural ventilation through opening

Table 2.

Existing construction materials thermal properties in Design Builder E+

Element

Materials

Width

(cm)

Materials properties

U-Value

(W/m2-K)

Internal

heat

capacity

(kj/m2-k)

Conductivity

W/m²-k

Specific heat

capacity

j/kg-k

Density

kg/m²

Roof

Al. deck 2.0 45.2 500 7824

3.84

93.2 Foam slag 5.0 0.25 960 1040

Al. deck 2.0 45.2 500 7824

External

walls

Cement

mortar and

plaster

2.0

0.35 840 950

1.619

144.9 Red brick 24.0 0.85 840 1500

Cement

mortar and

plaster

2.0

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Element

Materials

Width

(cm)

Materials properties

U-Value

(W/m2-K)

Internal

heat

capacity

(kj/m2-k)

Conductivity

W/m²-k

Specific

heat

capacity

j/kg-k

Density

kg/m²

Internal

partitions

Cement

mortar and

plaster

2.0 0.35 840 950

2.55

158.8 Red brick 12.0 0.85 840 1500

Cement

mortar and

plaster

2.0 0.72 840 1760

Floor

Marble tiles 2.00 3.5 1000 2800

2.49

216.24 Cement

mortar

2.00 0.72 920 1650

Sand ~6.00 2.00 1045 1950

Reinforced

concrete

15.00 2.5 1000 2400

Ground

Floor

Marble tiles 3.00 3.5 1000 2800

1.113

194.8

Cement

mortar

2.00 0.72 920 1650

sand ~6.00 2.00 1045 1950

Cast concrete 10.00 1.13 1000 2000

Insulting

material

2.00 0.04 1400 15

Rammed soil 1.2 880 1460

Ceiling

Cement

Plaster

2.00 0.35 840 950

2.49

Reinforced

concrete

15.00 2.5 1000 2400

Door Painted

Wooden

4.00

3.00

Windows

glazing

Single

glazing

0.6

5.77

Aluminum

framing

6.00

3. Results and discussion

3.1. Comparison between simulation results and monitored data

Real measurements for the temperatures and humidity, which are collected from the

case study classroom in 22nd

of June, are compared to the simulation results as seen in Fig.

10 and Fig. 11. The computer model was built as close as possible to the real case

including construction materials, glazing, and shading. The base case takes into account

the same parameters of “day-simulation”, shown in Table 1, i.e., the internal gains from

solar radiations (incidence through windows), lighting and occupancy level.

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As mentioned before, Energy Plus simulation tool has been validated by many researches

and specially in Cairo region [10]; nevertheless, this comparison is carried on only to ensure

its effectiveness in this case study. Fig. 10 and Fig. 11 show that the simulation results, for

the same day of investigations, reached near levels to the monitored data. However, there is a

slightly deviation of the simulation results from the measurement data.

Fig. 10. “day- simulation”: Simulated indoor space temperature versus monitored data for a

summer school day 22nd

of June

Fig. 11. “day- simulation”: Simulated internal humidity versus monitored data for a summer school day 22nd

of June

According to Rahman et al. (2008), it has been shown that if the difference between

measured readings and simulation results is less than 5% then the modeling procedure can

be described as a valid one[2]. Hence, for this case study, the validation error is calculated

to be approximately 4.37%, which is less than the validity range. This encourages the

authors to guarantee the simulation tool effectiveness when used in the classroom annual

investigations, the main concern of this paper.

3.2. Annual thermal comfort simulation results

The authors concern the annual thermal comfort investigations as the main objective of

this paper in order to estimate the space thermal performance throughout an academic year.

The input simulation parameters are being fixed and based on real annual aspects. Results

concerns: annual mean indoor air temperature, average annual predictive mean vote model,

annual discomfort hours, and average annual internal heat balance. From the annual

simulation results and the data conducted, which are explained in the next sections, one

can predict the annual cooling loads needed for the building.

3.2.1. Annual mean indoor air temperature Energy Plus simulation results, in Fig. 12, present the annual mean indoor air temperature

of the classroom base case study. This indoor air temperature affects directly the students’

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thermal comfort. According to ASHRAE Standard 55 [6], Adaptive Comfort Standard

(ACS) in this case is calculated to be in the range of 23.5-28°C. It is shown in the same

figure that about 45% of the annual temperature values are above 28°C, which is considered

the upper limit of the comfort range. Moreover, around 30% of the annual temperatures are

below 23.5°C, which is considered the lower limit of thermal comfort range during winter.

Fig. 12. Annual mean air temperatures for the base case

3.2.2. Annual predicted mean vote model Predicted Mean Vote model (PMV) is one of the most recognized thermal comfort models,

it is originally introduced by Fanger, ISO 7730 and ASHRAE 55 standards [8]. The PMV is an

index that predicts the mean value of the votes of a large group of persons on the 7-point

thermal sensation scale, based on the heat balance of the human body. According to ASHRAE

55 standards, the acceptable thermal comfort range for a PMV lies between -1 and +1. Average

annual PMV was calculated for the classroom case study using E+ depending on the

parameters of metabolic rate, occupancy rate, and clothing, in addition to the mean indoor air

temperature and humidity (which were estimated from E+ simulations). Figure 13 predicts the

average monthly PMV during a complete academic year for the classroom case study.

Fig. 13. Annual indoor PMV in classroom base case results

Annual PMV results in the Fig. 13 show that the maximum PMV estimated in summer

reaches a maximum discomfort of +2.5 in July, whilst the minimum PMV is estimated in

winter to be -1.7. The average PMV during the summer months is about +1.8 which

indicates a high level of thermal discomfort in the classroom. PMV comfort level ranges of

-1≦ PMV ≦1 reaches in almost 35% of the total hours during the year. Hence, the

classroom space on average are estimated to be thermally discomfort for about 65% of the

year which is considered a very high percent.

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3.2.3. Annual discomfort hours Energy Plus tool can predict the annual working hours distribution analysis for the

classroom case study. Figure 14 shows that there are annually about 3200 hours in which the

classroom temperature is at or above the 26°C, where as it is including about 2600 hours

annually with a temperature at or above the 32°C. The most important index in these values is

that there are annually about 3100 hours in which the temperature is equal to or above the

temperature 28°C which is the maximum comfort range. This means that there are about 3100

hours exceeding the comfort level in summer months including the annual vacation. By

subtracting August month hours (as it is considered the annual vacation) from the

investigations, one will figure out that the number of hours more than the comfort temperature

level, i.e., the 28°C, are about 2765 hours throughout a whole academic year. As a conclusion,

the number of the annual discomfort hours presents about 35% of whole academic year hours

and about 76% of the total summer school days hours. This percentage is considered to be very

high ratio of the year, which leads us to think about solutions that can be included in the future,

buildings in order to decrease the number of annually discomfort hours.

Fig. 14. Annual temperature distribution results

3.2.4. Annual internal heat gain balance Heat gained into the space is resulting from three sources: heat radiated from the

occupants bodies, heat conducted from the external fabrics through glazing and walls, and

through direct solar energy entering the space through window openings. While, the heat

lost due to its absorption by thermal mass or by convection through using alternative

cooling systems. The positive values indicate an increasing in space heat gains and

therefore increase in cooling loads, while the negative values present the loss of internal

heat and; therefore, the reduction of cooling loads. Figure 15 presents the annual hourly

heat gain and loss in the classroom case study through fabric and occupants. Where June

and July are having less occupants than the rest of the year, as they are considered in the

summer school days in which the occupants level is minimized to 50 % and school hours is

until 12:30 pm, and August is the annual vacation.

Thermal balance is obtained when the internal heat production in the space is equal to

the heat loss from the space. In this classroom case study, Fig. 15 indicates an extreme

increase in the internal heat gain through exterior windows and occupants throughout the

academic year. It shows also that the walls thermal mass absorbs a small percentage of the

internal heat gain. The average annual internal heat gain balance is about 261.6 kW/m².

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This high level of annual internal heat gain will result in high need of annual cooling loads.

Results indicate the importance of introducing alternative glazing materials in order to

block solar radiations. Additionally, it needs new construction composites to absorb excess

internal heat gain. Finally, the results show the necessity of having new passive and/or

active cooling systems in order to achieve thermal balance in the future buildings.

Fig. 15. Annual hourly heat gain balance through building fabrics and occupants

4. Conclusion and recommendations

This paper investigates the thermal comfort conditions for an existing naturally

ventilated public primary school in Nasr city region in Cairo governorate in Egypt. A

classroom in the second floor is selected to be as a base case study for all the investigations

carried in this paper. Measuring and recording of the classroom air temperature and

humidity all over a summer school day from 8:30 am until 02:30 pm, using Elitech

tempreture–humidity data logger (model URC-4HC), has been presented. The outputs of

measurements indicate a high level of thermal discomfort within the primary public school

classrooms in the typical summer day, in which the measurements were recorded. The

main contribution of this paper concerns modeling and numerically simulating the thermal

performance of the classroom case study by Design Builder modeling with Energy Plus

simulation tool. Annual thermal performance simulations are done for the case study in

order to predict the yearly average indoor air temperature, average annual Predicted Mean

Vote (PMV) model, annual number of discomfort hours, and annual heat balance. The

main achievements of this study are as follows:

The acceptability ratio of thermal comfort calculated by (ACS) model ranges from

23.5ºC to 28ºC. In this case, it has been found that 45% of the mean indoor

temperatures are more than the comfort range limit throughout the academic year.

The average PMV across the classrooms is +1.8 in summer months, which indicate a

high level of thermal discomfort.

Annual discomfort hours (more than 28°C) are about 2765 hours, which is about 35% of the

total hours throughout the whole academic year (excluding the annual summer vacation).

The average annual internal heat gain balance is about 261.6 kWh/m2, which means

a high level of cooling loads.

Therefore, the annual simulation results indicate a high level of thermal discomfort and

high annual cooling loads. These findings indicate the importance of integrating passive

cooling alternative strategies or energy efficient cooling systems into the classroom case

study in order to achieve the students’ thermal comfort. Recommended passive and active

strategies could be for further researches concerning:

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Passive alternative strategies:

Designing the school building according to environmental principals, e.g.,

considering the building form, orientation, use of thick or double walls, high

ceilings, green roofs and facades, opening percentage, skylights, shadings,

courtyards, wind catchers, etc.

Using advanced glazing materials, e.g., low e-glazing, smart windows, electro-

chromic glazing, etc.

Using alternative construction materials composites for building fabrics, e.g.,

renewable composites, Nano materials, earth composites, etc.

Integrating the internal spaces with phase change materials or boards in order to

stabilize the indoor mean air temperature.

Efficient active strategies:

Integrating energy efficient cooling systems, e.g., solar air conditioning, geothermal

cooling systems, chilled ceilings, etc.

Integrating active thermal storage systems that take the benefits of thermal mass and

the energy efficient cooling systems.

This research may assist designers to improve schools thermal performance trying to achieve the

students’ thermal comfort all over the academic year in future school buildings in Cairo, Egypt.

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359


ظروف الراحة الحرارية في المباني المدرسية القائمة في مصر استقصاء

ملخص

، وذرددب ستخددخ سوب وربات ددتث وور حتعددتة ورألساددت، وياول ورردد ى ورحدداو وربحثددت هدد ا ورى ددتحددس

ر س خت وسخسوئت حكىتت ف تحتفظت ورقتهاة ف تصا. وحسا ه و وربحد عدم تدل ورى دج حدم ورىلدىح ر اوحدت

ر طالب ف فصىرهم ورس وخدت الدالح ورألدتب ورس وخد ع دت. حألخبدا حودت تحتوردت ر ىلدىح رد ح دىح ورحاو ت

كل حن حألزز وراوحدت ورحاو دت فد ورلصدىح ورس وخدت. و ان دت ر دتذي ورك بدىحا ردس ت وور حتعدتة، فد ن هد ا

ت رس جتث ورحاو ة ورسوال دت ورى ت حشكل حوت حح ال ر ؤشاوث وراوحت ورحاو ت نل طاق ورقتختث ور سون

ر سة دىب تس خد عتتدل تدل ورردتنت 6105ووراطىست ف فصل ا وخ سسوالل ور س خت . حم ورقت ف ىنى

تألدتاة ورقتخدتث س خدتئل ور حتعدتا، و حدم ورخحقدق تدل لدحت نخدتئل جتردتل. و ح د 033:1لدبتحت وحخد 03:1

خل ن ت فتن دت ساندتتل ور حتعدتا رخخدخ سوب فد وخخقصدتل وياول ور حتعتة وورخأعس تل حنهت حاوة تىثىق سهت ت ت ن

ورى ت وربحثتورحاو ورر ى ،ورخ ه تصس وربح ورائر تل ه ا

هدد و و حألدداه هدد ا ورى ددت ، تددل الددالح ور حتعددتة ورردد ى ورحاو ددت ، وورخ بددؤ س خىخدد رددس جتث حدداو ة

حدت ورحاو دت، ندسا خدتنتث ندسب وراوحدت ورحاو دت ، و تخىخد ورهىول ف ويتتعل ور غ قت خ ىت، تخىخ وراو

وعخرتب ورحاو ة ورسوال ت ورر ىت. وحشا نختئل ور حتعتة وجىا ترخىي ندتح تدل ندسب وراوحدت ورحاو دت الدالح

٪ تدل خدتنتث ورأل دل وخ دتوز ورحدس وي صد 34ورألتب ورس وخ ع ت. وشا ورخح ل ورر ى حودت حن حدىور

ت ورحاو دت . وندالوة ن د ذردب، فد ن ور خدتئل حظهدا ن د تردخىي ندتح تدل تخىخد وعخردتب رس جتث وراوح

ورحاو ة ورسوال ت خ ىت طىوح ورألتب ورس وخ

ع رته ت ئرت ره ا ورى ت، خ ج نختئل ور حتعتة والنخبتا ر حه ت اتتي وخدخاوح تث ورخبادس وررد ب

و ا جددت ورحدداو ة فدد ويتددتعل ور غ قددت، وزددتاة وراوحددت ورحاو ددت حو حنظ ددت ورخباددس وركددأل تددل حجددل3 وخددخقا

ورطالب وحق ل تزون ورحاو ة ورسوال ت رخألزز وياول ورحاو ر بتن ور س خت ف ور رخقبل

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